/*
 * Copyright (c) 2010 by Intevation GmbH
 *
 * This program is free software under the LGPL (>=v2.1)
 * Read the file LGPL.txt coming with the software for details
 * or visit http://www.gnu.org/licenses/ if it does not exist.
 */

package de.intevation.gnv.raster;

/**
 * Generates label attributes for iso lines. It takes the
 * neighboring palette ranges and calculates the mid point
 * between these two ranges.
 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
 */
public class IsoAttributeGenerator
implements   IsoProducer.AttributeGenerator
{
    /**
     * The palette where to look for the ranges.
     */
    protected Palette palette;

    /**
     * Default constructor.
     */
    public IsoAttributeGenerator() {
    }

    /**
     * Constructor to create an IsoAttributeGenerator with
     * a given lookup palette.
     * @param palette The palette.
     */
    public IsoAttributeGenerator(Palette palette) {
        this.palette = palette;
    }

    public Object generateAttribute(int neighbor1, int neighbor2) {
        Palette.Entry e1 = palette.getEntryByIndex(neighbor1);
        Palette.Entry e2 = palette.getEntryByIndex(neighbor2);

        if (e1 == null || e2 == null) {
            return null;
        }

        double e1t = e1.getFrom();
        double e2f = e2.getTo();

        return Double.valueOf(e2f >= e1t
            ? 0.5d*(e1t+e2f)
            : 0.5d*(e2.getTo()+e1.getFrom()));
    }
}
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